A display device may be provided with a touch panel (also known as a touchscreen or touchscreen panel) as a user interface device enabling such operations as function selection and data input for a variety of apparatuses including personal computers. Such a touch panel display device may be provided in addition to or in lieu of the conventional input devices of a keyboard and mouse. Touch panels are suitable for a variety of applications where the display device itself may be used for system control or data entry, including retail settings such as point-of-sale systems (kiosks) and automated teller machines and in consumer electronics devices such as personal digital assistants and cellular telephones. Touch panels are essentially display overlays enabling the display device to display and receive information via the same screen, and conventional touch panels include many types, which are generally classified according to the methodology of the input, e.g., resistive, capacitive, surface wave, infrared, strain gauge, optical imaging, and acoustic pulse recognition. Each of these permits a stimuli that registers as a touch event.
For example, a resistive system registers a touch event whenever two resistive layers make contact, such that the stimulus may be any solid object, e.g., a human finger or a pencil eraser. A capacitive system, on the other hand, must have a conductive input, which is most typically supplied by a user's finger. The surface wave system, operating like the resistive system but using ultrasonic waves that pass over the touch panel, allows a touch event to be registered using any object that can effectively disturb the waves.
Touch panels are typically assembled together with the screen of a general display device, to operate in conjunction with touch driver software installed in the display device, i.e., pre-stored in its memory, to assign a function to each of a predetermined set of icons (or windows) acting as input keys arranged according to screen coordinates. A touch event for a currently displayed icon causes a corresponding operation, e.g., program execution or data entry. In other words, the touch driver serves as an interface with the personal computer and effectively executes in turn an operation for each touched icon (touch event). In doing so, a controller of the display device recognizes the coordinates of the touched icon, whereby a corresponding image is displayed on the touch panel's screen in response to a signal generated by the touch driver.
In many touch panel applications, user operation can be facilitated by displaying a minimum number of icons, which is disadvantageous since fewer icons places undesirable limits on the functionality of a system using a touch panel display device. To increase the number of simultaneously displayed icons for a given display device, however, icon size should be reduced, which exacerbates user operation and tends to contribute to inputting errors. In particular, icons may become too small for a consistent and accurate manipulation by a human finger, in which case the system experiences difficulty in recognizing a particular touch event as desired. Meanwhile, touch panel manufacturers report a 1.5% error rate in the specified screen dimensions in monitors and other display devices, which inhibits software design and application. Accordingly, contemporary touch panel display devices are disadvantageous in that selection and manipulation of a specific icon (currently displayed key) becomes more difficult, such that multiple attempts by a user may be required for smaller icons or icons that are unfavorably arranged, e.g., near an edge or in a corner of the screen where display accuracy may be degraded.